Thank you for taking the time to respond.
The studding must have been bent when Parcelforce people handled the tube.
It wasn't very bent but it WAS bent.
If the studding had been wrapped in sufficient bubble wrap to stop it moving it the tube it might NOT have been bent due to rough handling. But there was insufficient wrapping the first time and no wrapping or padding on the second attempt.
I have no way of knowing if the studding was bent when it left the supplier but, going by the damaged condition in which other items delivered by Parcelforce arrived here, the damage was caused by Parcelforce.
I bought #10-32 studding because that's the thread on my Taig lathe. Although a M5 nut will fit on a #10 bolt, it doesn't work the other way round.
If I had realised the problems that I would have buying #10 threaded items, I would have changed everything to M5 when I bought the lathe and saved a great deal of expense and stress
With best wishes and thanks again.
MC